Process for anionic polymerization in a continuous stirred tank reactor

ABSTRACT

Control of an anionic polymerization is obtained by monitoring an indicator of molecular weight of the polymer in the polymerizing mixture, measuring the molecular weight of the polymer produced therein and using this information to control the rate at which polymerization initiator is added to the polymerizing mixture in a continuous stirred tank reactor.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of application Ser. No. 071,496 filed July 9,1987, now abandoned, which is a divisional of application Ser. No.525,863, filed 8/24/83 now U.S. Pat. No. 4,725,654, which is a CIP ofapplication Ser. No. 364,959 filed 4/2/85, now abandoned.

The present invention relates to a novel process and apparatus for thecontrol of anionic polymerization reactions in a continuous stirred tankreactor. The term continuous stirred tank reactor refers to any reactorwherein material is continuously or continually added to the reactor andmaterial removed from the reactor at about the same rate as material isadded thereto. The contents of the reactor being maintained in agenerally homogeneous condition both from a composition and atemperature point of view. Thus, a continuous stirred tank reactor mayhave the configuration of conventional stirred cylindrical or sphericaltank, or it may be a loop wherein material is rapidly recirculatedwithin the loop. Polymerization is frequently carried out employing aplug flow reactor wherein the composition at the inlet end is verydifferent from that at the outlet end and a temperature gradient mayexist therein. Such is not true with a continuous stirred tank reactor.Oftentimes, it is desirable to prepare polymers employing anionicinitiators in a continuous stirred tank reactor wherein monomers ormonomer and optionally a diluent are continuously added and anionicpolymerization initiating compound is also continuously added, thematerial being removed from the reactor containing solvent and polymer.Volatile materials are generally removed from the polymer and thepolymer formed into pellets for further processing. A highly desirablecharacteristic for commercial polymers is uniformity of both thecomposition and molecular weight. If a process produces polymer ofvarying molecular weight at different times, it involves considerableexpense and labor to store the different molecular weight polymers andthen blend various batches to provide a material with apparentuniformity. Various attempts have been made to control anionicpolymerization by means of colorimetric devices, on the assumption thatif the color of the polymerizing material is the same, the molecularweight of the product must be uniform. This assumption is believed to bein error, as the sensitivity of the colorimeter may vary over extendedperiods of time. Impurities in monomer, diluent and the like may varywith time as well as the effective amount of the initiator being fed tothe reactor. A number of attempts at colorimetric control have beenmade, some of which are set forth in the following U.S. Pat. Nos.:2,066,934; 2,897,247; 2,977,199; 3,290,116; 3,468,972; 3,476,729;3,553,295; 3,743,629; 3,804,593. Oftentimes, variations in molecularweight between batches of a polymer can result in many difficulties inthe fabrication thereof. Oftentimes in the preparation of polymers bycontinuous and batch polymerization, particularly alkenyl aromaticpolymers, gels are formed during the polymerization. Such gels arereadily recognized on the extrusion of the polymer into strands. Strandscontaining significant amounts of polymer gel are characterized by agenerally lumpy nature, that is the strands have regions of increasedand decreased diameter. Gel containing polymers which are extruded intostrands or filaments exhibit lumps or sub-like formations, the numberper unit length being generally proportional to the gel content. Suchgel containing polymer is generally unsuited for extrusion because ofthe visible irregularities in the final product. Gel containing polymersare usually not suitable for injection molding as generally the finalproduct shows surface irregularities which deviate from theconfiguration of the mold.

It would be desirable if there were available an improved method for thecontrol of anionic polymerization.

It would also be desirable if there were available an improved methodfor the control of anionic polymerization which provided a product of agenerally constant average molecular weight over long periods of time.

It would also be desirable if there were available an improved methodfor the continuous anionic polymerization of alkenyl aromatic polymerswhich would produce a generally gel free product.

It would also be desirable if there were available an improved apparatusfor the preparation of polymers by anionic polymerization which wouldprovide a product of a generally constant molecular weight.

These benefits and other advantages in accordance with the presentinvention are achieved in a method for the polymerization of ananionically polymerizable alkenyl aromatic monomer whereinpolymerization of the polymerizable monomer is initiated by anorganometallic anionic polymerization initiating compound whereinpolymerization of the monomer takes place in a continuous polymerizationstirred tank reactor wherein polymerization components are continuouslyadded to the reactor and reaction mixture discharged from the reactor atabout the same rate as materials are added to the reactor, to therebyprovide a product which is generally gel free.

A particularly desirable embodiment comprises providing a first signalwhich varies with the molecular weight of polymer in the effluent fromthe reactor, the first signal altering the rate of polymerizationinitiator addition to the reactor to maintain a generally constantmolecular weight of the polymer, measuring the molecular weight of thepolymer thereby obaining a second signal, employing the second signal tocompensate a first signal generating means for drift or error in thefirst signal generating means to thereby maintain a generally uniformmolecular weight of the polymer in the reactor effluent.

Also contemplated within the scope of the present invention is anapparatus for the preparation of anionically polymerized alkenylaromatic polymers, the apparatus comprising in cooperative combination amonomer supply means, a monomer flow control means associated with adischarge of the monomer supply means, an anionic polymerizationinitiator supply means, an initiator flow control means in associationwith a discharge of the initiator supply means, a continuously stirredtank reactor having an inlet and an outlet, the inlet of the continuousstirred tank reactor being in operative communication with the monomerflow control means and the initiator flow control means and adapted toreceive material therefrom; a discharge conduit connected to thedischarge of the continuously stirred tank reactor, the dischargeconduit being in operative communication, a means to provide a firstsignal which varies as molecular weight of polymer in effluent from thecontinuously stirred tank reactor varies, the first signal adjusting theinitiator flow control to thereby provide molecular weight control of apolymer being prepared, means to measure the molecular weight of apolymer and provide a second signal indicative of the molecular weightof the polymer, means to receive the second signal and adjust the meansto provide a first signal to thereby provide a polymer of a generallyuniform molecular weight.

By the term alkenyl aromatic monomer is meant an anionicallypolymerizable monomer composition containing at least 50 weight percentof monomer having the formula: ##STR1## wherein R is hydrogen or methyl,Ar is an aromatic ring structure having from 1 to 3 aromatic rings withor without alkyl substitution wherein any alkyl group contains 1 to 6carbon atoms, any remaining monomer being monomeric material anionicallycopolymerizable with the alkenyl aromatic monomer. Typical alkenylaromatic monomers which may be used alone or in admixture with oneanother include: styrene, α-methylstyrene, vinyl toluene, all isomers,paratoluene being preferred, ethyl styrene, all isomers, propyl styrene;tertiarybutylstyrene, octylstyrene, vinylnaphthalene, vinyl biphenyl,vinyl anthracene and the like, and mixtures thereof.

Anionic polymerization is well known in the art as are anionicpolymerizations wherein a color change occurs when polymerization takesplace under the influence of an anionic initiator. Representativepolymerization systems are set forth in the following U.S. Pat. Nos.:2,975,160; 3,030,346; 3,031,432; 3,139,416; 3,157,604; 3,159,587;3,231,635; 3,498,960; 3,590,008; 3,751,403; 3,954,894; 4,183,877;4,196,153; 4,196,154; 4,200,713; 4,205,016; the teachings of which areherewith incorporated by reference thereto.

Generally, it is desirable to conduct polymerization in accordance withthe present invention in the presence of an inert solvent for thepolymeric material being formed. The choice and proportion of solventused, if any, will depend on the availability of the solvent, theparticular reactor heat transfer characteristics, ease ofdevolatilization of the reactor effluent and the like. Typical solventsinclude benzene, toluene, ethyl benzene, ethyl toluene alone or inadmixture with minor amounts of alkyl compounds, such as cyclohexane andthe like. Generally, the amount of solvent utilized is dependent on themolecular weight of the polymer produced and the mixing ability of thereactor. Usually in the practice of the present invention it isdesirable to maintain uniformity of temperature and composition in thereaction mixture within the polymerization vessel during the period whenabout 99 weight percent of the monomer is converted to polymer. It isdesirable that the temperature of the reaction mixture be maintained at±3 degrees centigrade throughout the reaction mixture and preferablywith ±11/2 degrees centigrade. In order to obtain the desiredtemperature and composition uniformity in a recirculating coil reactor,such as the reactor described in U.S. Pat. No. 3,035,033 to Schweitzer,Jr., et al, the volume of material circulating within the coil should beat least 15 times and preferably 25 times the volume of material beingadded to and discharged from the coil. In the case of a stirred tank,the temperature and composition of the reaction mixture should begenerally uniform at all locations within the reaction mixture exceptthat of the region adjacent the point of monomer feed which is within 10percent of a minor dimension of the tank in the region of the monomerfeed point. For the case of a 40 inch diameter tank, 80 inches inheight, having an axially disposed agitator being fed monomer radiallyinwardly through a side of the tank at the bottom, the temperature andcomposition of the reaction mixture should be generally constant at alllocations within the reaction mixture contained within the tank at alocation more than four inches from the point of feed. In general, thegreater the mixing, the more uniform the product obtained, and thechance of gel formation minimized.

The means for generating the first signal may be any of a variety ofsensors which generate a signal indicative of molecular weight of thepolymer. Generally, in anionic polymerization, the polymerizing mixtureprovides a colored anion, for example, as in the polymerization ofstyrene employing an organolithium initiator, a strong red coloration isinduced which is more or less proportionate to the number of end groupspresent and therefore is indicative of the molecular weight of thepolymer. A viscometer is also useful as is an analysis of the number ofend groups present. In polymerization done in accordance with thepresent invention, generally conversion of monomer to polymer exceeds 99weight percent, and due to the nature of a continuous stirred tankreactor and the rapidity of the polymerization, the solids level isgenerally constant. For each 1% solids variation in the reaction mixturefor polystyrene of about 300,000 molecular weight, the molecular weightwill vary about 4,000 gram moles, thus providing a great latitude forthe means to generate the first signal. The means to generate the secondsignal desirably is a device which actually measures the molecularweight of the product in the reaction mixture and provides essentially astandard against which the output of the means to generate the firstsignal can be compared. Any of a variety of devices may be employed asmeans to generate the second signal such as a viscometer, lightscattering and the like. However, the preferred embodiment of thepresent invention is to employ a gel permeation chromatograph whichalternately measures the molecular weight of the polymer in the reactionmixture and a standard polymer of known molecular weight to therebyprovide maximum reliability.

FIG. 1 schematically represents on embodiment of the invention.

FIGS. 2 and 3 schematically represent a sampling procedure of thearrangement of FIG. 1.

In FIG. 1 there is schematically depicted an apparatus suitable for thepractice of the method of the present invention, the apparatus isgenerally designated by the reference numeral 10. The apparatus 10comprises in cooperative combination a supply tank 11 having an inletconduit 12, an inlet conduit 13 and an outlet conduit 14 in which thereis disposed a pump 15. The conduit 14 is in communication with a waterinlet conduit 17. Both conduits 14 and 17 discharge into a conduit 18having a heat exchanger 19 disposed therein. The conduit 18 dischargesinto a cracking column 21. The discharge from the cracking column 21 isto a conduit 23 having heat exchanger 24 therein, a decanter 25, aconduit 26 for the discharge of water and an organic material receivingtank 27. Organic material from tank 27 is forwarded to a distillationcolumn 29 through conduit 28. The distillation column 29 has overheaddischarged lines 31 and 32. Discharge conduit 31 has a heat exchanger 33disposed therein. Conduit 31 connects to and discharges into conduit 32.Distillation column 29 has a discharge conduit 35 and recirculationconduit 36 having heat exchanger 37 disposed wherein. Conduit 35discharges to a second distillation column 38 having overhead dischargeconduits 39 and 41, as well as bottoms circulation system similar tocolumn 29. Conduit 39 has a condenser 42 disposed therein. Conduit 41has disposed therein liquid storage tanks 43 and 44. Tanks 43 and 44 areconnected in series. Conduit 41 terminates at a continuous stirred tankreactor 46. The reactor 46 has an inlet 47 and a discharge 48. Thereactor 46 has the configuration of a closed loop having a pump 46atherein to provide agitation or circulation of liquid within the reactor46. An anionic polymerization initiating composition supply tank 51 isin communication with conduit 41 by means of conduit 52. Conduit 52 hasdisposed therein a flow control means or variable speed pump 53. Thedischarge opening 48 of the continuously stirred tank reactor 46 is inoperative combination with conduit 55. Within conduit 55 is disposed ameans 56 to provide a signal which varies with the molecular weight ofpolymer contained in material flowing through line 55. Also, disposedwithin the line 55 is a means 57 which provides a first signal whichvaries as the molecular weight of the material flowing in line 55varies; for example, a color detector. A control means 58 is inoperative combination with means 56, 57 and pump 53. Conduit 55 remotefrom discharge 48 discharges to a terminating stirred reactor 61. Alsoconnected to terminating stirred reactor 61 is an inlet conduit 62 and adischarge conduit 63 having disposed therein a pressure control valve64. Conduit 63 discharges to a devolatilizing apparatus 65. Thedevolatilizing apparatus 65 has a bottoms discharge conduit 66 and anoverhead discharge conduit 67. Within line 67 is a quality indicatingmeans 68, such as an infrared spectrometer

In FIG. 2, there is schematically depicted a sampling arrangement forthe determination of molecular weight of a polymer from a polymerizer46a discharging to a line 55a. As depicted in FIG. 2, a conduit 71 is inselective communication with line 55a. The conduit 71 discharges to amixing chamber 72 which beneficially is of small volume and has disposedtherein an agitator 73. Advantageously, the agitator 73 is magneticallyactivated. the chamber 72 has associated therewith a nitrogen or otherinert gas supply conduit 74 and a vent conduit 75. The conduits 74 and75 each have a valve disposed therein. The mixing chamber 72 dischargesinto the conduit 77 to a gel permeation chromatograph. The conduit 77has a valve disposed therein. A standardizing polymer supply means 78has associated therewith a valved conduit 79 which is connected to a gelpermeation chromatograph 81. The line 77 from chamber 72 alsocommunicates with a gel permeation chromatograph. As depicted in FIG. 2,a suitable solvent such as tetrahydrofuran at a pressure of 60 poundsper square inch gauge is pumped through the gel permeationchromatograph. Material from the polymerizer 46a passes through line 55a and through a four-way valve 82.

In FIG. 3, the four-way valve 82 has been repositioned so that a portionof the material flowing through line 55a passes through conduit 71 tothe mixing chamber 72 and is passed through the gel permeationchromatograph 81.

Although the apparatus and method of the present invention can beemployed to provide a wide variety of polymers and copolymers, FIG. 1depicts an arrangement which is particularly suited for the preparationof polystyrene from ethylbenzene. Ethylbenzene is provided to conduit 12and is stored in tank 11, passed through line 14 and pump 15 to conduit18 where it is admixed with water and heated in heat exchanger 19 toprovide a mixture of ethylbenzene and steam which in turn is passedthrough the cracking column 21. The effluent from the cracker is passedthrough line 23 and heat exchanger 24 where the effluent is cooled. Theeffluent from the cracker column after cooling is passed to thedecanting vessel 25 and water is discharged from the conduit 26. Crudestyrene passes from the decanting vessel to crude styrene tank 27. Fromthe tank 27 crude styrene is conveyed through conduit 28 to distillationcolumn 29. Distillation column 29 serves to remove low boilingcontaminants such as benzene, toluene and residual water. The bottomfraction from first distillation column 29 passes through line 35 withsome recirculation and heating through line 36 and heat exchanger 37.Conduit 35 discharges a fraction consisting primarily of ethylbenzeneand styrene into distillation column 38. The high boiling fractionconsisting primarily of tars and cymene is discharged from the bottom ofdistillation column 38. The overhead fraction from the seconddistillation column is passed to conduit 41 and through tanks 43 and 44to the reactor 46. The overhead fraction is a mixture of about equalparts of ethylbenzene and styrene. After being admixed with an anionicpolymerization initiator from conduit 52 and pump 53, effluent from thecontinuously stirred tank reactor 46 is discharged through conduit 55and the detectors 56 and 57. Conduit 55 discharges into anothercontinuous stirred tank reactor 61 wherein the polymer is admixed withethanol to deactivate the polymer. The effluent from reactor 61 ispassed through conduit 63 and pressure control valve 64 into thedevolatilizer 66 wherein ethylbenzene is removed and molten polystyreneis removed from the devolatilizer 65 through conduit 66.

The molecular weight detector 56 provides a signal to a computer 58, thesignal being indicative of the weight average molecular weight of thepolymer. The color detector 57 also provides a signal to computer 58 andthe computer in turn adjusts the set point of the color detector 57 toobtain a generally constant molecular weight polymer. The computer 58also provides a signal to the pump 53, to thereby provide a desiredquantity of the anionic initiator to maintain the desired weight averagemolecular weight. In practical applications usually continuousmonitoring of the molecular weight is not necessary. From a practicalstandpoint, the molecular weight should be monitored at least aboutevery 8 hours and the set point of the color detector adjustedaccordingly. Preferably, the molecular weight and set point adjustmentis made every two hours. The molecular weight arrangement 56a asdepicted in FIGS. 2 and 3 permits the intermittent sampling of theproduct stream, dilution of the fixed quantity of the stream, thedilution occurring in the chamber 72, and the material is passed througha gel permeation chromatograph such as 81. To assure close control ofthe molecular weight of the product and accuracy of the results from thegel permeation chromatograph, a standard is employed. That is, asolution of polymer of known molecular weight and distribution is passedthrough the gel permeation chromatograph for calibration purposes. Gelpermeation chromatography is the preferred method of determiningmolecular weight; however, other techniques may be utilized, such asmelt flow, solution viscosity, light scattering, and vapor phaseosmometry and the like.

In the practice of the present invention, it is desirable that theresidence time of material in the reactor be from about 1 to about 3hours. If the residence time is less than 1 hour, molecular weightcontrol becomes difficult and if the residence time is greater thanabout 3 hours, the process becomes less economical. It is highlydesirable that the polymerization temperature be maintained betweenabout 80° and about 140° C. If the temperature is below about 80° C.,the quantity of initiator employed becomes excessive and if thetemperature is greater than about 140° C. the conversion of monomer topolymer decreases. The weight percentage of polymer to solvent in thereactor should be between about 30 and 80 weight percent. If the solidscontent of the reactor is below about 30 weight percent, excessivesolvent must be removed to recover the polymer and when the solidscontent of the rector is above about 80 weight percent, the viscosity ofthe reaction mixture is higher than can be handled by most practicalprocessing equipment. The solvent generally desired is an alkyl aromaticmaterial. Most commercially used is ethylbenzene. However, xylene,toluene and the like may be employed. When one considers the feed streamto the reactor for lithium initiated polymerizations, the oxygen contentshould be held to less than 1 part per million (hereafter ppm) by weightbased on the weight of the total feed stream of oxygen. If the oxygencontent of the stream is greater than about 1 ppm, it adversely affectsthe color of the polymer recovered from the reactor. Similarly, water,if present, should be present in an amount less than 10 ppm as it alsoadversely affects the color of the polymer recovered from the reactor.Active hydrogen, organic compounds such as acetylenes andoxygen-containing organic impurities should be maintained at a level ofless than 60 ppm. Such materials also adversely affect the color of thepolymer. The recovered polymer should contain less than 20 ppm oflithium as the presence of lithium also adversely affects the color ofthe invention. A principle advantage of the process of the presentinvention is that polymers with a very low degree of yellowness can beprepared employing low levels of lithium initiator. Desirably,polymerization in accordance with the present invention utilizes theconversion of monomer to polymer greater than 99 weight percent ofmonomer plus polymer present in the reactor at any point. Generally, abatch polymerization for the use of the plug flow reactor results inpolymers of increased yellowness when compared to polymers prepared inaccordance with the present invention. The batch and plug flow reactorsgenerally require greater quantities of lithium containing initiatorthan does the method of the present invention.

The invention is further illustrated but not limited by the followingexamples:

EXAMPLE 1

Apparatus was employed generally in accordance with FIGS. 1 through 3.The cracker had three sections: a pre-heating section about 4 feet longfilled with ceramic Beryl saddles, a 2 foot long cracking section havingan hourly space velocity of 2.14 reciprocal hours and was filled with acracking catalyst commercially available under the trade designation ofShell 105 containing ferric oxide. The cracking temperature was about625° C. and the pressure was about 5 pounds per square inch gauge. Inthe third section of the cracker, the temperature was reduced to about300° C. The first two cracker sections were heated by ceramic heaters,each about 2500 watt capacity and the ratio of water to ethylbenzene wasabout 0.9. The condenser equivalent to condenser 24 was water cooled.Between the condenser 24 and the decanter 26 was a gas liquid separator25 which was a flat vessel about 30 cubic inch capacity. From the gasliquid separator crude styrene was pumped from a tank equivalent to tank27 into the first distillation column. The first distillation column wasabout 2 inches in diameter and packed to provide in excess of 40 heightequivalent of theoretical plates and was employed to remove the lightfraction from the crude mixture. Benzene, toluene and water were theprimary materials removed. The bottom fraction from column 1 was fed tothe second distillation. The first distillation column was operatedunder a pressure of 130 millimeters of mercury and had a bottomtemperature of about 90° C. and a reflux ratio of about 5:1. The seconddistillation was 4 inches in diameter, packed and had 40 heightequivalent of theoretical plates. The second distillation column wasoperated under a pressure of 110 millimeters of mercury and atemperature of about 85° C. bottom. The reflux ratio was 6:1. Theoverhead composition removed from the second distillation column was amixture of styrene and ethylbenzene in about a one to one ration.Bottoms were principally tars and para-cymene. Both columns had aresidence time of about 2 hours. The storage vessels equivalent to tanks43 and 44 had a residence time of about 24 hours. Both tanks weremaintained under an atmosphere of nitrogen having a pressure of about 20pounds per square inch gauge. Impurities other than styrene andethylbenzene were maintained at a level below a hundred parts permillion by weight. Material from the tank 44 was forwarded to acontinuously stirred tank reactor 46 by means of a double-headedone-quarter inch Milton-Roy piston pump. The reactor was a recirculatingcoil constructed of one-inch inside diameter 316 stainless steel tubingconnected in a square configuration. The tubing was jacketed and heatedwith hot water. The contents of the stainless steel tubing reactor werecirculated therein using a Northern gear pump, stock No. 4448, operatingat about 200 rpm. The internal volume of the reactor was 1867 cubiccentimeters. The gear pump was located adjacent the inlet of theethylbenzene and initiator and downstream thereof to provide promptmixing of the initiator and feed mixer with the viscous polymerizingmass recirculating within the reactor. Pressure in the reactor wasmaintained at 50 pounds per square inch gauge by manipulation of apressure control valve, such as valve 64 of FIG. 1. The polymerizationinitiator employed was normal-butyllithium which was purchased as a 15%solution in heptane and prior to use was diluted with toluene to providea normal-butyllithium concentration of from about half to one percent byweight. The pump employed to forward the normal-butyllithium was aMilton-Roy piston pump driven by a variable speed electric motorcontrolled by a computer.

The computer program employed was as follows:

    ______________________________________                                        f0: *Z+1→Z                                                             f1: *sfg); spc2;p                                                             rt "Valves off                                                                ot";cfg1; cfg3;s                                                              fg8                                                                           f2: *sfg0; spc2;p                                                             rt"Color contro                                                               1 off at";cfg                                                                 f3: *sfg0; spc2;p                                                             rt "Mw control                                                                off at;cfg3                                                                   f4: *sfg0; cfg10;                                                             prt"PF Cntrl Of                                                               f at"                                                                         f5: *→X; sfg5                                                          f7: *→V[X];sfg6                                                        f11: *if V[3]*12                                                              >=360 and I>V[2                                                               0]+130; V[3]*12-                                                              2→I                                                                    f13: *sfg0; spc2;                                                             prt"Valves on a                                                               t";sfg1;"stand                                                                by "→BS                                                                f14: *sfg0;spc2;                                                              prt"Color contr                                                               c1 on at";sfg2                                                                f15: *sfg0;spc2;                                                              prt"Mw control                                                                cn at";sfg 3                                                                  f16: *sfg0;sfg10                                                              ;prt"PF Cntrl o                                                               r at"                                                                         0: "Anionic Polymerization Control Program w/GPC;                             Patent Case";                                                                 1: "#'s 2-16, Initializes hardware&software";                                 2: dim B$[20],AS[14],D[150],T[150],V[35],M[7],W[7],F[7],                      CS[20],C[3]                                                                   3: "Initializes variables, loads sp. function keys";                          4: -3 I;3}r;2}Z;1}R;sfg 7;trk 1; ldk 1;gsb "time"                             5: "Calls for needed variables, clears 723 bus";                              6: gsb " assign";rds(723)}J; on err "error"                                   7: "fmt#1 for relays,#2 for A/D;#3 for D/A;#4 for display";                   8: fmt 1,"0140TG",fz4.0,"T",z                                                 9: fmt 2,c,z;fmt 3,c,f4.0,c,z;eir 7                                           10: "Clears D/A card";                                                        11: wrt 723,2,"0120TD0000TD2000TD4000TD6000T"                                 12: "#'s 14-16 initialize clocks";                                            13: "U1 for int/detect., U2 for int/valves,U3 count/detect.";                 14: wrt 9,"A, U1=,U1=01,U2=,U2=02,U3=13,Ur=14"                                15: wrt 9,"U1P3000/U2P5000"                                                   16: oni 9,"clock";eir 9;wrt 9,"U2G"                                           17: "#'s 19-44,main display loop";                                            18: "Display for sampling system";                                            19: if Z=1 and flg1;dsp BS,D,V[3]-I/12,K                                      20: if Z=1 and not flg1;dsp "Sampling system is off,"                         21: if not flg2 and flg3; "Mw Ctrol"}CS                                       22: if not flg2 and not flg3; "Color Ctrl"}CS                                 23: if flg2 and not flg3;"Ctrl off"}CS                                        24: "Display for control mode & parameters";                                  25: if Z=2;dsp CS,H,V[5],r32/5.11                                             26: if Z=3;dsp "Term. trans.=",P                                              27: "Display for GPC data";                                                   28: if flg1 and Z=4 and A/2-int (A/2)=0;fxd 0;dsp "Last Mw=",r21              29: if flg1 and Z=4 and A/2-int(A/2)#0;dsp "Last MWD=",r22                    30: if not flg1 and Z=4;dsp "GPC is off,"                                     31: "Display for MWD control";                                                32: "Flg 5 set by SF Key, denotes operator variable change";                  33: if flg5;gsb "variables"                                                   34: "Flg 9 set by peak-end,enables GPC calc";                                 35: if flg9;gto "GPCcalc"                                                     36: "Flg 0 set by SF Key, denotes var.change,gives time";                     37: if flg0;wrt 9,"R";red 9,AS;prt AS;c11` assign`;spc 2;cfg 0                38: "Shut down of valves";                                                    39: if r50=1;wrt 9,"U1HU3HU3C";wrt 723.1,0,0}K}D;-5}I                         40: if r50=1;wrt 723.3,"0140TD",2000,"T";wrt 723.3,"0140TD",                  6000,"T";0}r50                                                                41: "End of loop";                                                            42: if Z>6;2}Z                                                                43: fxd 2;gto 19                                                              44: "GPCcalc";cfg 9;gsb "time"                                                45: prt "GPC Calculation";dsp "GPC Calc. in Progress"                         46: "Finds peak start (S) by weighted avg.";                                  47: V[1]}r5                                                                   48: for J=V[9]+15 to V[9]-1 by - 1                                            49: if J=V[9]and 3*V[1]<r5;prt "No peak-start found."gto "peak error".        50: if J=V[9];1.1r5 r5;15 +V[9]}J;gto 48                                      51: if D[J]+2*D[J-1]+D[J-2]<=D[J-1]+2*D[J-2]+D[J-                             3]+r5;g to 53                                                                 52: next J                                                                    53; J-1}S;V[2]}r6                                                             54: "Finds peak end (F) by wrighted avg.";                                    55: for J=V[10]-15 to V[10]+1                                                 56: if J=V[10]and 3*V[2]<r6;prt "No peak-end found."gto "peak error"          57: if J=V[10];1.1r6}r6;V[10]-15}J;gto 55                                     58: if D[J]+2*D[J+1]+D[J+2]<=D[J+1]+2*D[J+2]+D[J+                             3]+r6;gto 60                                                                  59: next J                                                                    60: J+1}F                                                                     61: "Calc. slope (M) and intercept (B) of baseline";                          62: (D[F]-D[S1]/(T[F1-T[S])}M                                                 63: D[S]-M*T[S]}B                                                             64: "Subtracts baseline off of peak & checks for neg. values";                65: for J=S to F                                                              66: D[J]-M*T[J]-B}W                                                           67: if J<S+5 and W<=O and J#S;J}S;g to 62                                     68: if J>F-5 and W<=0 and J#F;J}F;g to 62                                     69: next J                                                                    70: for J=S to F;D[J]-M*T[J]-B}D[J]                                           71: next J                                                                    72: "checks peak size & prints peak data";                                    73: if max (D[*])>18;prt "Peak too large";gto "peak error"                    74: if max (D[*])<2;prt "Peak too small";gto "peak error"                     75: prt "Peak-height is",max(D[*])                                            76: fxd 0;prt "Peak-start is",S;prt "Peak-end is",F                           77: gsb "Sum"                                                                 78: "If std., bypass Mw calc.&control";                                       79: if K=0;0}r9;gto 108                                                       80: "Calc. Mn,Mw,MWD";                                                        81: r4*r7/r5}r20;r4*r6/r73}r21;r4*r11/r6}r12;r21/r20}r22                      82: wrt 723.3,"0140TD",dto((r21-VI301)/(V[31]-V[30])*500)+                    2000,"T"                                                                      83: wrt 723.3,"0140TD",dto((r12-V[32])/(V[33]-V[32])*500)+6000,"T"            84: "If not Mw control,bypass";                                               85: if not flg3;g to 93                                                       86: "Check of sample Mw dev. & first samp";                                   87: if abs(r21-r35)>V[16]and r35#);prt "Mw dev.";gto 93                       88: "Calc. %trans.change";                                                    89: V[18]*(r21-V[4])/1000/r33                                                 90: "Calc. new % trans. setpoint";                                            91: V[5]-r33/V[5];r21}r35                                                     92: "Round-off Mn,Mw data";                                                   93: r20*.001}r20;r21*001}r21;r12*.001}r12                                     94: if r20-int (r20)>=.5;r20 +1}r20                                           95: if r21-int(r21)>=.5;r21 +1 r21                                            96: if r12-int(r12)`>=.5;r12+}r12                                             97: int(r20)*1000}r20;int(r21)*1000}r21;int(r12)*1000}r12                     98: "Printer output of Mw data";                                              99: fxd 0;prt "Mn=",r20;prt "Mw=",r21;prt "Mz=",r12                           100: fxd 2;prt "Mw/Mn=",r22;prt "Mz/Mw=" ,r12/r21                             101: "If Mw control, prt new setpoint";                                       102: if flg3;prt "New s.p.=",V[5]                                             103: "If report mode on, prt";                                                104: if flg10;gsb "report"                                                    105: "End of calc,return to dsp loop";                                        106: 0}D}T;gto 19                                                             107: "Check if old calib. holds";                                             108: if abs(r5*6/r7 2-V[11])<.001;gto 118                                     109: "#'s 119-127 calib. calc., successive iteration";                        110: if r5*r6/r7 2-V[11]>=0;gto 113                                           111: 1.05r8}r8;gsb "Sum"                                                      112: gto 110                                                                  113: if abs(r5*r6/r7 2-V[11]<.0001;gto 118                                    114: if r5*r6/r7 2-V[11]<0;r8}r9;r10}r8;.5(r8-r9)+r9}r8;gto 116               115: r8}r10;.5*(r8-r9)+r9}r8                                                  116: gsb "Sum"                                                                117: gto 113                                                                  118: V[12]*r7/r6}r4;fxd 3;prt "Calib. constants"                              119: "Printer output of calib.";                                              120: fxd 0;prt "C1=",r4,fxd 3;prt "C2=",r8;0 D}T;gto 19                       121: "Summing loop for Mw calc.";                                             122: "Sum";0}r5}r6}r7}r11                                                     123: for J=S to F                                                             124: exp(r8*T[J])}E                                                           125: r5+D[J]*E}r5;r6+D[J]/E}r6;r7+D[J]}r7;r11+D[J]/E 2}r11                    126: next J;ret                                                               127: "Routine for reset of valves loop upon error";                           128: "peak error";if K#0;gto 19                                               129: 0}K}D}T;-8}I;wrt 723.1,24;gto 19                                         130: "Allows offline input of Mw data";                                       131: "offline";                                                               132: "Adjusts %trans. setpoint";                                              133: V[5]-V[i8]*(V[19]-V[ 4])/10000}V[5]                                      134: prt "New (ol)s.p. =",V[5];ret                                            135: prt Valves is relay writing routine for GPC cycle time                   <30 min.";                                                                    136: "I is 5 sec. counter, K is sample counter";                              137: "valves":I+1}I;if I=V[3]*12;0}I                                          138: if K=0 and I=0;wrt 723.1,40;"Inject std. "}BS                            139: if K>0 and I=V[28];wrt 723.1.14;"Inject sample"}BS                       140: if K=0 and I=4;wrt 723.1.200;"Running std."}BS                           141: if K>0 and I=4;wrt 723.1.224                                             142: if K=V[15]and I=5;"Last sample"}BS                                       143: if K>0 and I=5;wrt 723.1,20                                              144: if K<V[15]and I-V[3]*12-118;wrt 723.1.1;                                 "Sample coil"}BS                                                              145: if K<V[15]and I=V[3]*12-116;wrt 723.1.100;"Stirring"}BS                  146: if I=V[17]+4;wrt 9,"U3GUIG",0}L                                          147: if I=V[20]+4;wrt 9,"U1HU3HU3C";sfg 9                                     148: if K<V[15] and I=V[3]*12-6;wrt 723.1,0;"Stir stop"}BS                    149: if K<V[15]and I-V[3]*12-2;wrt 723.1,4                                    150: if I=V[3]*12-I;K+1}K;if K=V[15]+1;0}K                                    151: ret                                                                      152: "Longvalves is for GPC cycle 30 min.";                                   153: "Std/samp/wait/std/samp/wait . . . order";                               154: "longvalves";I+1}I;if I=V[3]*12;-2}I                                     155: if I=-2:wrt 723,1,40;"*Inject std."}B$;0}K                               156: if I=3:wrt 723.1,200;" *Running std."}B$                                 157: if I=4;wrt 723,1,1;"*Sample coil"}B$                                     158: if I=5;wrt 723.1,0                                                       159: if I=6;wrt 723.1,1                                                       160: if I=7;wrt 723.1,100;"*Running std."}B$                                  161: if I=V[17]+3;wrt 9,"U3GU1G";0}L                                          162: if I=V[20]+3:wrt 9,"U1HU3HU3C";sfg 9                                     163: if I=120;wrt 723.1,0;"*Sample ready"}B$                                  164: if I=122;wrt 723.1,4                                                     165: if I=127-V[28];wrt 723.1,14;"*Inject samp."}B$                           166: if I=127;wrt 723,1,224                                                   167: if I=128;wrt 723,1,20;"*Running samp."}B$                                168: if I=V[17]+127;wrt 9,"U3GU1G",wrt 723.1,4000;0}L                         169: if I=V[20]+127;wrt 9;"U1HU3HU3C";wrt 723.1,0;1}K;sfg 9                   170: if I=V[20]+128;"*Waiting"}B$                                             171: ret                                                                      172: "Clock determines which clock (3 or 5 sec) interrupts and branches"      173: "Accordingly, Also contains red for polycolor, termcolor,IR";            174: "clock";wrt 9,"T";rdb(9)}Q;eir 9                                         175: if bit(0,Q);c11 `detector`;gto 189                                       176: if not flg1 or flg 7:gto 179                                             177: if bit(1,Q) and V[3]*12<360;gsb "valves"                                 178: if bit(1,Q) and V[3]*12>=360;gsb "longvalves"                            179: A+1}A;if A=V[27];0 A                                                     180: if A#0;gto 189                                                           181: C[2]}C[3];C[1]}C[2];C}C[1]                                               182: wrt 723.2,"O160TA13TO260TAX"red 723,C;otdC/40}C                          183: "This avgs. polycolor over 4 readings for Report";                       184: (C+C[1]+C[2]+C[3]/4}H                                                    185: wrt 723.2,"O160TA12TO260TAX";red 723,P;otdP/40}P                         186: "if color cntrl is on, branches":                                        187: if not flg2;gsb "control"                                                188: "Clears 1B bus & multiprogrammer":                                       189: if rds (723)=64:eir 7                                                    190: iret                                                                     191: "Detector reads GPC detector, running clock, and                         stores data";                                                                 192: "detector";L+1}L;eir 9                                                   193: wrt 723.2,"O160TA11TO260TAX"                                             194: red 723,D;wrt 9,"U3V";red 9,T;T/60000}T                                  195: otdD}D;D*.005}D;D} D[L];T}T[L]                                           196: ret                                                                      197: "Supplies display for operator variable change";                         198: "variables";if flg5;gsb "time";cfg 5                                     199: if X=1;dsp "Peak-start sensitivity factor?"                              200: if X=2;dsp "Peak-end sensitivity factor?"                                201: if X=3;dsp "GPC cycle time (min.)?"                                      202: if X=4;dsp "Mw setpoint?"                                                203: if X=5;dsp "% transmittance setpoint?"                                   204: if X=6;dsp "Controller gain?"                                            205: if X-7;dsp "Reset constant?"                                             206: if X=9;dsp "Minimum peak elution time?"                                  207: if X=10;dsp "Maximum peak elution time?"                                 208: if X=12;dsp "Molecular weight of standard?"                              209: if X=12 ;dsp "Molecular weight of standard?"                             210: if X=13;dsp "Min. cat. pump speed (%)?"                                  211: if X=14;dsp "Max. cat. pump speed (%)?"                                  212: if X=15;dsp "# of samples between std.?"                                 213: if X=16;dsp "Mw error deviation?"                                        214: if X=17;dsp "Clock-start counter?"                                       215: if X=18;dsp " %trans. adjust, constant?"                                 216: if X=19;dsp "Enter off-line Mw data!"                                    217: if X=20;dsp "Clock-stop counter?"                                        218: if X=21;dsp "New cat. pump speed (%)?"                                   219: if X=27;dsp "Read cycle (5 sec.inc.)?"                                   220: if X=28;dsp "Injection time (5 sec. inc.)?"                              221: if X=30;dsp "Mw Molytek zero?"                                           222: if X=31;dsp "Mw Molytek max.?"                                           223: if X=32;dsp "Mz Molytek zero?"                                           224: if X=33;dsp "Mz Molytek max.?"                                           225: if X=0;ret                                                               226: if not flg6;jmp 0                                                        227: c11 `print`;ret                                                          228: "Control of NBL pump from %trans. deviations":                           229: control";                                                                230: H-V[5]}r30;r30*V[6]+r31}r32                                              231: if r32<V[13]*5.11;V[13]*5.11}r32                                         232: if r42>5,11*V[14];V[14]*5.11}r32                                         233: if flg4;gto "pumps"                                                      234: r3i+r30*V[7]}r31                                                         235: if r31>V[14]*5.11;V[14]*5.11}r31                                         236: if r31<V[13]*5,11;V[13]*5,11}r31                                         237: "pumps";wrt 723.3, "0140TD",dtor32, "T"                                  238: ret                                                                      239: "Routine for printing time of variable change":                          240: "time";wrt 9,"R";red 9,AS;spc 2;prt AS;ret                               241: "Output of report data after GPC calc.";                                 242: "report";fxd 2                                                           243: prt "Pump speed=",r32/5.11                                               244: prt "% trans.=,"H;spc 2;ret                                              245: "Checks to see if all needed var. are assigned";                         246: "whenever control mode change is made.";                                 247: "assign";                                                                248: if flg2;gto 255                                                          249: if V[5]=0;5}X;gsb "variables"                                            250: if V[6]=0;6}X;gsb "variables"                                            251: if V[7]=0;7}X;gsb "variables"                                            252: if V[13]=0;13}X;gsb "variables"                                          253: if V[14]=0;14}X;gsb "variables"                                          254: if V[27]=0;27}X;gsb "variables"                                          255: if not flg1;gto 272                                                      256: if V[3]=0;3}X;gsb "variables"                                            257: if V[1]=0;1}X;gsb "variables"                                            258: if V[2]=0;2}X;gsb "variables"                                            259: if V[9]=0;9}X;gsb "variables"                                            260: if V[10]=0;10}X;gsb "variables"                                          261: if V[11]=0;11}X;gsb "variables"                                          262: if V[12]=0;12}X;gsb "variables"                                          263: if V[15]=0;15}X;gsb "variables"                                          264: if V[17]=0;17}X;gsb "variables"                                          265: if V[20]=0;20}X;gsb "variables"                                          266: if V[28]=0;28}X;gsb "variables"                                          267: if V[30]=0;30}X;gsb "variables"                                          268: if V[31]=0:31}X;gsb "variables"                                          269: if V[32]=0;32}X;gsb "variables"                                          270: if V[33]=0;33}X;gsb "variables"                                          271: cfg 7                                                                    272: if not flg3; gto 276                                                     273: if V[4]=0;4}X;gsb "variables"                                            274: if V[16]=0;16}X;gsb "variables"                                          275: if V[18]=0;18}X;gsb "variables"                                          276: ret                                                                      277: "Supplies printed copy of operator variable change"                      278: "print";cfg 6 fxd 0                                                      279: if X=1;fxd 3;prt "Upslope factor=",V[ ]                                  280: if X=2;fxd 3;prt "Downslope fact.=",V[2]                                 281: if X=3;prt "GPC cycle time=",V[3]                                        282: if X=3 and V[3]*12>=360;sfg 8;prt "override to longvalves";beep          283: if X=4;prt "Mw set point=",V[4]                                          284: if X=5;fxd 2;prt "%transmittance setpoint=",V[5]                         285: if X=6;fxd 3;prt "Controller gain=",V[6]                                 286: if X=7;fxd 3;prt "Reset constant=",V[7]                                  287: if X=9;prt "Min. peak time=",V[9]                                        288: if X=10;prt "Max. peak time=",V[10]                                      289: if X=11;fxd 2;prt "MWD of std.=",V[11]                                   290: if X=12;prt "Mw of std.=",V[12] ;V[12]}r1}r2                             291: if X=13;prt "Min. cat speed=",V[13]                                      292: if X=14;prt "Max. cat speed=",V[14]                                      293: if X=15;prt "Samp. cycle=",V[15]                                         294: if X=16;prt "Mw dev. limit=",V[16]                                       295: if X=17;prt "Clock start=",V[17]                                         296: if X=18;fxd 3;prt "% trans. adjust. constant=",V[18]                     297: if X=19;prt "Off-line Mw=",V[19]; gsb "offline"                          298: if X=20;prt "Clock stop=" ,V[20]                                         299: if X=21;fxd 2;prt "Pump speed=",V[21];V[ 21]*5.11 r31                    300: if X=27;prt "Read cycle=",V[27]                                          301: if X=28;prt "Inject time=",V[28]                                         302: if X=30;prt "Mw Molytek zero=",V[30]                                     303: if X=31;prt "Mw Molytek max.=",V[31]                                     304: if X=34;prt "Mz Molytek zero=",V[32]                                     305: if X=33;prt "Mz Molytek max.=",V[33]                                     306: 0}X;spc 2;ret                                                            307: "error";wrt 723.1,4000;wait 15000;wrt 723.1,0;stp                        *1106 -- --                                                                   ______________________________________                                    

In the computer program, Statements 2-16 initialize all variables andclear all cards. The real-time clock is set up for use and is started.Statements 19-43: these statements control the display of the 9825. Thisdisplay can be changed by the operator by pressing special function key(SFK) f1 on the computer. Statements 44-126: these statements calculatethe Mw of the polymer from the detector readings. This segment isexecuted when all the readings are collected and is under control of thevalve subroutine. Statements 88-91 are those that actually modify thecolorimeter-initiator addition rate control loop. Statements 98-100print the Mw information on the paper tape. Statements 130-134: thissubroutine allows offline input of Mw; that is, the operator can inputMw information from another outside source (e.g., another GPC) andmodify the colorimeter-initiator addition rate control loop. Statements135-171: these statements contain the subroutines "valves" and"longvalves". "Valves" controls the GPC sampling valves when the GPCcycle is less than 30 minutes. This control is accomplished throughwriting to the relay card and turning specific relays on and off. Thisin turn, opens and closes Whitey* ball valves by supplying power toASCO* solenoid valves through the relays. The length of the GPC cycle isdefined as how often Mw information is received, that is, how often asample is prepared and run through the GPC. The frequency ofstandardization (how many samples follow a standard) can be variedthrough variable V[15]. In addition, the GPC cycle (V[3]) can be variedin 5 second increments. The other variables involved with thissubroutine control the injection time, V[28], and when the computer"looks" at the GPC detector for the elution of the injected sample,V[17] and V[20]. "Longvalves" has all of the above features with someminor changes: (1) it is used for GPC cycle times greater than 30minutes and (2) it allows only the sample cycle of std, sample, std,sample . . . Statements 172-190: the subroutine "clock" does twoimportant things. First, it decides upon interrupt, what the real-timeclock is signalling must be read from the outputting instruments.Secondly, it reads the input signal, either from the colorimeter or theGPC detector. Subroutine "detector" is used for reading the GPCdetector. Statements 228-238: this is the colorimeter controlsubroutine. This routing calculates the continuously changing initiatoraddition requirements based on the anion concentration in the reactoreffluent. It then outputs a new voltage on the D/A card to change therate of addition. This is done by varying the amount of power suppliedto the motor which runs the initiator addition pump. The computeroutputs a 0-10 V signal to a PARAJUST* motor controller, which in turnthen varies the power output to the motor. Special Function Key Tape:this is a printed copy of the statements which are stored in the specialfunction keys of the computer. These statements allow operation controlover the mode of control, variable value, display, etc. These statementsare stored on a cassette tape and loaded into the memory of the computerin statement #4 (trk 1, ldk 1).

It should be noted that not all of the statements of the computerprogram were employed.

EXAMPLE 2

A feed stream was purified by pumping a 1 to 1 by weight mixture ofstyrene and ethylbenzene using a double-headed Milton-Roy pump. Themixture was prepared through a heat exchanger which raised thetemperature to 55° C. The heated stream was discharged through a spraynozzle into a receiver which had an internal pressure of 20 millimetersof mercury. Spraying into the receiver served to remove oxygen and mostof the water present; about 1.5 weight percent of the stream was lost.From the receiver, the feed materials were passed through a molecularsieve commercially available under the trade designation of Linde 3A,the bed of molecular sieve at a length to diameter ratio of 18 and avelocity of 5 parts of the stream per par of sieve by weight per hour.The resultant feed material contained styrene and ethylbenzene in abouta 1 to 1 ratio, less than 1 ppm of oxygen; less than 3 ppm of water;less than 5 ppm benzaldehyde; less than 5 ppm styrene oxide; less than 5ppm of acetophenone; and about 40 ppm of phenylacetylene. The purifiedstyrene ethylbenzene feed stream was pumped to a polymerizer employing adouble-headed 1/4" Milton-Roy pump. The polymerizer was a 2-litergenerally cylindrical reactor, commercially available under the tradedesignation of Parr, and a hollow auger agitator, the hollow augercomprising a cylinder slightly shorter in length than the interior ofthe auger and slightly smaller in diameter. A land was helicallydisposed on the outside of the cylinder. The land was sized such thatthe cylinder generated by rotation of the hollow cylinder and land wasslightly less than the internal volume of the reactor. Such an agitatoris described in U.S. Pat. No. 4,239,863, the teachings of which areherewith incorporated by reference thereto. Hot water under pressure wasemployed to heat the reactor to 95° C. The purified feed stream andinitiator were introduced into the side of the reactor at a rate to givea two-hour residence time. The initiator was normal-butyllithium pumpedat a rate to provide about 60 ppm. The pressure within the reactor wasmaintained at about 50 pounds per square inch gauge using a pressurecontrol valve at the outlet. The stream from the reactor was fed to aterminator coil of 1 inch inside diameter, 316 stainless steel tubingconnected in a square configuration and having an internal volume ofabout 467 cubic centimeters. Material was recirculated within theterminator coil using a Northern gear pump stock No. 4448 operating atabout 200 revolutions per minute. A solution of 1 weight percent ethanolin ethylbenzene was fed to the terminator coil at a rate about twicethat of the normal-butyllithium fed to the polymerizing vessel. Effluentfrom the terminator coil was then pressure fed into a devolatilizerequipped with a flat plate heater and a screw extruder such as describedin U.S. Pat. No. 3,014,702, the teaching of which is incorporated byreference thereto. The exterior of the heater was maintained at apressure of about 35 millimeters of mercury and the reaction mixtureheated to a temperature of about 240° C. to provide a polymer containing0.8 weight percent volatiles. The molecular weight of the resultantpolymer over a 24-hour period was maintained at plus or minus 5,000 of210,000 grams/mole. The color of the product was excellent and had ayellowness index of 0.007.

EXAMPLE 3

A styrene ethylbenzene mixture about 1 to 1 by weight was purifiedgenerally as in Example 1 except on a larger scale, approximately 1,000times larger than that of Example 1. The molecular sieve bed had alength to diameter ratio of 40 to 1 and a velocity of 2.5 parts of feedper part of sieve by weight. The purified feed stream is analyzed tohave about 42 weight percent styrene, 58 weight percent ethylbenzene andthe following contaminants: less than 1 ppm oxygen; less than 5 ppmwater; about 34 ppm phenylacetylene; less than 14 ppm acetophenone; lessthan 5 ppm benzaldehyde; less than 5 styrene oxide. A polymerizationvessel was used which comprised a 500 gallon tank having a condensermounted vertically above the vessel. The condenser had 157 square feetof cooling surface. The vessel and condenser were supported on weighingcells, the output of which was employed to control the volume of thereaction mixture within the polymerization vessel. A vacuum system wasemployed to provide a reduced pressure within the vessel. Vapor removalwas utilized to maintain desired polymerization temperature. A variablespeed pump was mounted on the bottom of the vessel to remove polymersolution therefrom, the speed of the pump being varied to maintain agenerally constant polymerization vessel weight. The polymerizationvessel was fitted with a hydraulically driven agitator rotating at about100 revolutions per minute. Condensate from the condenser was recycledto the feed stream. The polymerization vessel was operated under thefollowing conditions: a reactor inventory of 1500 pounds; a feed rate of850 pounds per hour; a residence time of 13/4 hours; the temperature ofthe reaction mixture 100° C; a reactor pressure of 237 millimeters ofmercury; normal-butyllithium 80 ppm based on the total weight of thefeed; resulting in a product containing 21 ppm lithium and having ayellowness index of 0.029. For a 24-hour period, the weight averagemolecular weight as determined by gel permeation chromatography was195,000 plus or minus 10,000. The reaction was terminated by passing thereaction mixture through a section of 1.5 inch pipe containing fiberoptic probes and side stream takeoff port which led to gel permeationchromatograph. The reaction mixture was then passed to a section of6-inch jacketed pipe containing eighteen 6"×8" static mixing elementscommercially available from Koch Engineering Company. The jacket washeated to a temperature of about 120° C. and a 5 weight percent solutionof ethanol in ethylbenzene was pumped into the reaction mixture prior toits entering the static mixers at 4 opposing points generally displacedabout 90° from adjacent points on the pipe at a flow rate of about 5pounds per hour. After termination, partial polymer was devolatilizedusing two devolatilizers in series, the first devolatilizer operating at160° C. and 600 millimeters of mercury and the second devolatilizer at240° C. and 20 millimeters of mercury.

EXAMPLE 4

The procedure of Example 2 was repeated with the following exceptions.The feed mixture to the reactor was 42 parts by weightparamethylstyrene, 2 parts by weight paraethyltoluene and 56 parts byweight ethylbenzene. The rate of feed was one reactor volume in a periodof one and one-half hours. The polymerization temperature was 80 degreescentigrade. The weight average molecular weight of the product obtainedover a period of 24 hours was about 340,000±30,000 grams per mole.Extrusion of the resultant polymer through a strand die provided astrand with no visible lumps or gels. The product was suitable forextrusion and injection molding of high quality articles.

COMPARATIVE EXAMPLE 1

The procedure of Example 2 was repeated with the exception that theagitator was not rotated. Over a period of 24 hours the best control ofmolecular weight that was obtained was about ±100,000 grams per mole. Onextrusion of the product a yellow strand was obtained which containedlarge lumps or gels. A molded product from such a strand has poor colorand surface appearance.

COMPARATIVE EXAMPLE 2

A 1/2 inch diameter 30 inch long jacketed tubular reactor was equippedwith a color measuring device and gel permeation chromatograph asdescribed in Example 1. The inlet end of the reactor was fed with amixture of styrene and ethylbenzene (1:4 by weight), together with apolymerization initiating amount of normal-butyllithium at a ratesufficient to provide a residence time of 15 minutes. Atmospheric steamwas applied to the jacket. Temperature sensing probes disposed withinthe reaction mixture in the reactor indicated the temperature range wasabout 20 degrees centigrade. Employing the temperature and a gelpermeation chromatography signal to control the reaction resulted inproduct varying ±100,000 grams per mole from average over a 24-hourperiod. The effluent from the reactor contained large visible gels. Theproduct was not useful as a good quality material for extrusion orinjection molding.

COMPARATIVE EXAMPLE 3

A vertical stirred tube reactor was employed having an inside diameterof 6.5 inches and a useful internal length of about 55 inches and avolume of about 0.907 cubic feet. The reactor was jacketed into threeabout equal zones, each zone having a thermocouple projecting into thereaction mixture. The top driven agitator had a shaft diameter of oneinch and 51/4 inch straight arms spaced 21/2 inches apart on theagitator shaft. A plurality of 1/2-inch diameter fixed rods projectedradially inwardly into the reactor for a distance of 2.43 inches. Thefixed rods interdigitated with the agitator arms on rotation of theagitator. The reactor had a total heat transfer area of 11.16 squarefeet. The physical arrangement of the reactor was such that the axis ofrotation was vertically disposed. The reaction mixture had excellentmixing in planes normal to the axis of the reactor and the agitatorshaft while top to bottom mixing was very poor to nonexistent, resultingin what may be considered a plug flow reactor. A pump by means of anexternal line was connected between the top and bottom of the reactor.The pump was capable of recirculating the contents of the reactor at arate of 7.5 times per hour. Equal parts by weight of styrene andethylbenzene purified as in Example 2 and a polymerization initiatingamount of a normal-butyllithium solution were pumped into the top of thereactor. The reactants were fed to the reactor at a rate of one-halfreactor volume per hour for a residence of 2 hours. The followingtemperature relationships were observed:

    ______________________________________                                        Polymer Temperature °C.                                                                 Jacket Temperature °C.                                Feed Middle    Discharge Feed   Middle                                                                              Discharge                               Zone Zone      Zone      Zone   Zone  Zone                                    ______________________________________                                        99   101       100       101    67    85                                      ______________________________________                                    

In a 24-hour period of operation, the weight average molecular weightcould not be maintained closer than plus or minus 50,000 grams per mole.The major amount of polymerization appears to occur in the middle zoneof the reactor. On extrusion of the product as a strand, gels or lumpswere observed. The polymeric material produced is unsatisfactory forextrusion or injection molding.

In a manner similar to the foregoing examples of the invention, otheranionic polymers are readily prepared and the molecular weight of thepolymers controlled.

As is apparent from the foregoing specification, the present inventionis susceptible of being embodied with various alterations andmodifications which may differ particularly from those that have beendescribed in the preceding specification and description. For thisreason, it is to be fully understood that all of the foregoing isintended to be merely illustrative and is not to be construed orinterpreted as being restrictive or otherwise limiting of the presentinvention, excepting as it is set forth and defined in thehereto-appended claims.

What is claimed is:
 1. In an anionic polymerization process wherein areaction mixture comprising an anionically polymerizable monomerselected from the group consisting of alkenyl aromatic monomers andmixtures thereof as the sole polymerizable monomer and an organometallicanionic polymerization initiator is subjected to polymerizationconditions and the resulting polymeric product is thereafter recovered,the improvement comprising conducting the polymerization in a continuousstirred tank reactor wherein monomer and initiator are continuouslyadded thereto, said reactor operating at a temperature between about 80°C. and about 140° C., a conversion of at least 99 weight percent, and asolids content from about 30 to about 80 weight percent.
 2. A processaccording to claim 1, wherein the reaction mixture additionallycomprises an inert solvent.
 3. A process according to claim 2, whereinthe solvent is an alkyl aromatic material.
 4. A process according toclaim 1, wherein the initiator is an organolithium initiator.
 5. Aprocess according to claim 1, wherein the temperature and compositionare maintained generally uniform throughout the reaction mixture.
 6. Aprocess according to claim 1, wherein the temperature is maintained at±3° C. throughout the reaction mixture.
 7. A process according to claim1, wherein the conversion exceeds 99 weight percent.
 8. A processaccording to claim 1, wherein the residence time of material in thereactor is from about 1 to about 3 hours.
 9. A process according toclaim 1, additionally comprising the step of providing a signal whichvaries with the molecular weight of the resulting polymeric product toalter the rate of polymerization initiator addition to provide a polymerof generally constant molecular weight.
 10. A process according to claim1, wherein the alkenyl aromatic monomer is styrene.
 11. A continuousanionic polymerization process for polymerization of a reaction mixtureconsisting essentially of an alkenyl aromatic monomer, ethylbenzene andan organometallic anionic polymerization initiator the steps of theprocess comprising continuously adding the reaction mixture to acontinuous stirred tank reactor operating at a temperature between 80°C. and 140° C., a conversion of at least 99 weight percent and a solidscontent of 30 to 80 weight percent and continuously recovering theresulting polymeric product.
 12. A process according to claim 11 whereinthe alkenyl aromatic monomer is styrene.
 13. A process according toclaim 11 wherein other ingredients of the reaction mixture besidesalkenyl aromatic monomer, ethylbenzene and initiator are maintained at alevel less than 100 ppm.